Nude Turntable Project

Hi Gary,
Very interesting improvements and co-incidentally.......I have been testing and analysing the 'weakness' with the nude Victor as well.
As you have discovered.....the thin perforated metal circular surround is, I fear, the Achilles heel to supporting the Victors on spikes?
With the Technics SP10 models (as Chris has shown)..... it is possible (and preferable) to fit custom long tube spikes to the underside of the platter surround itself whereas it is exceedingly difficult to do with the Victors?
The problem is structure-borne feedback as is mostly the case with turntables?
Every supporting shelf is under 'stress' to some degree depending on its material, thickness and load, but most importantly.......on the 'span' and 'type' of span.
In my case with the wall-mounted shelf.........the cantilevered nature plus the heavy load and wood core structure sets up a particularly 'nasty' stress pattern.
What I have recently discovered is that 'stress' in any material....... creates a subsonic 'sound-field' within that material which is directly related to the 'level' of stress.
I previously thought.....wrongly I must admit.....that lower frequencies could not 'bridge' the pointy end of a spike support?
It is now known that they can and that spikes in fact 'couple' rather than 'de-couple'.
The 'stress-induced' sound waves in my cantilevered shelf are being transferred to the thin metal surround of the Victor which in turn passes them on the platter surround, motor and spindle support which the stylus then 'reads'?
This can be verified by placing the stylus on a record without turning on the motor......and then turning up the volume of the preamp until one can induce a loud low-frequency feedback loop through the speakers.
You, Gary.....have tackled the problem at the resultant culprit.....the metal surround which can work well.
I am going to attempt to tackle the problem at the 'source' by trying to prevent the transfer of this 'sound field' between shelf and turntable by isolation devices.
I'll keep you posted......:^)

Halcro, I see all improvements as cumulative. I agree that the shelf can have a huge effect and must be addressed. And it MAY be a good idea to support the TT at the original support ring. But no matter what else you improve, if you don't damp the tin-can you will still have problems. Even if you decide (heaven's forbid) to go back to a plinth even a wonderful slate and unobtanium plinth, you need to damp that can. I would also damp the chamber under the platter.

By the way, no matter how high I set the volume I don't get feedback. $7 and two hours and you will be much happier.

Gary

Dear Aigenga: A coincidence with your latest tweck: years ago I made it the same with my Denon's DP75/DP80, even I did it with both Denon platters ( the down side. ). I used sorbothane and works great I did it too with the MS RX5000 platter with good success too.

Now, I posted somewhere ( not in this thread. ) that I used a damping fluid/paint that was used several years ago to damp internally speakers ( it apply as a paint. In my speakers I think I gave it like 2-3 layers of that " paint " and works wonderful. ). Well I used with the Denonn's motoer covers to damp it and works really good too.
One " advantage " in the Denons is that that motor cover is not made it of one piece but three different ones and in some way when these parts were atached together trhough screws it damps in some way each to the other vibrations or at least change the frequency resonance and intrude the less on the final performance.
The other experience I had and have with this very similar Denon/Victor is that " still points "/metal like footers does not damp almost nothing and at least in my set up the pneumatic AT footers are way better.

Regards and enjoy the music,
R.

Raul, I was thinking about a paint solution but decided that I had the space to use this 3M product and that it would be even more effective.

I have the pneumatic AT footers under my pre-amp and I used to have them under my TT (I also used squash balls at one point)but decided that I didn't want any rubber creating a flexible suspension so I went with the cones. I don't expect them to damp anything but do hope that they will couple the TT to the granite and drain some vibrations from the TT.

The platter on the JVC already has a ring of rubber-like material on it from the factory. I was afraid of putting anything additional on the platter for fear of effecting the balance.

Your idea of the motor cover is an excellent one and I will gladly borrow it and dampen the motor cover on my TT as well. Thanks.

Halcro and Gary:

In this thread (here), dgad and dgarretson suggested using springs underneath the platform that supports the tt. The thought was that one could control the frequency at which the platform moves by calculating the load on the spring. Choosing a lower freq outside the audible range will ameliorate your issue, Halcro? I have no idea how to do the calculation but this should be kinderspiel for an architect.

I haven't myself tried it, but I did something similar (I believe) when I had my sp10 on spikes resting on a sandbox which was in turn supported by 4 AT 616's (which are just fancy springs?). That set up was a great improvement over what I had before. I was going to buy the springs to test whether they could give me the same results--but for far cheaper than the 616's.

McMaster-Carr has a bunch of different springs for different loads and compression rates: here